Plating copper on aluminum

ABSTRACT

Copper is electroplated on aluminum by immersing an aluminum workpiece into an aqueous alkaline plating bath containing a divalent copper salt and a complexing agent consisting of a mixture of an amine and ammonia in predetermined proportions, and passing an electric current through the bath between the aluminum workpiece as cathode and an anode which is generally but not exclusively of copper. This process produces uniform and adherent deposits of copper on aluminum with a current efficiency in the neighborhood of 100 percent. It can be used with advantage for a continuous plating of wires, strips, sheets and other sufficiently malleable aluminum objects and for batch plating of any aluminum workpiece.

' nited States tel harucha et al.

PLATING COPPER ON ALUMINUM Inventors: Nanbhai Rustomji Bharucha, Laval,

Quebec; Mohammad Barakat Ilahi Janjua, Pointe Claire, Quebec, both of Canada Canada Wire and Cable Company Limited, Toronto, Ontario, Canada Filed: Mar. 9, 1972 Appl. No.: 233,361

Assignee:

Foreign Application Priority Data Nov. 10, 1971 Belgium H0362 US. Cl. 204/28, 204/4], 204/52 R, 204/DIG. 2

llnt. Cl. C23b 5/60, C23b 5/50, C23b 5/18 Field of Search 204/38 B, 4], 52 R, 204/28, DIG. 2

References Cited UNITED STATES PATENTS 2/1959 Miller 204/38 B 12/1964 Wells et al. 204/52 R 3,280,736 10/1966 Schafler et al 204 41 FOREIGN PATENTS OR APPLICATIONS 822,628 10 1959 Great Britain 204 52 R 116,447 10/1958 U.S.S.R 204/52 R Primary Examiner-F. C. Edmundson Att0rney-Ge0rge I-I. Spencer et a1.

[57] ABSTRACT Copper is electroplated on aluminum by immersing an aluminum workpiece into an aqueous alkaline plating bath containing a divalent copper salt and a complexing agent consisting of a mixture of an amine and ammonia in predetermined proportions, and passing an electric current through the bath between the aluminum workpiece as cathode and an anode which is generally but not exclusively of copper. This process produces uniform and adherent deposits of copper on aluminum with a current efficiency in the neighborhood of 100 percent. It can be used with advantage for a continuous plating of wires, strips, sheets and other sufficiently malleable aluminum objects and for batch plating of any aluminum workpiece.

49 Claims, No Drawings PLATING COPPER ON ALUMINUM The present invention relates to electroplating of copper on aluminum. The plating ofcopper on aluminum using an aqueous alkaline electroplating bath which contains a copper salt and a complexing agent consisting of an amine, is not new. Suchprocess, however, has several disadvantages. The adherence of copper on aluminum, for example, is not entirely satisfactory and the current efficiency isclearly insufficient. Tests have also been made to plate copper on aluminum using an aqueous alkaline bath based on a complex of copper and ammonia. However, these tests have not produced desired results because copper deposits obtained thereby were found to be very hard and brittle at high current densities, while forming a black smut with very little adherence at low current densities. I

It was therefore suprising to find that an aqueous alkaline electroplating bath comprising divalent copper salt and a complexing agent consisting of a mixture of ammonia and of a primary, secondary, or tertiary amine, in predetermined proportions, leads to a substantially improved plating of copper on aluminum.

Thus, according to the main embodiment of the present invention, it has been found that the use of an aqueous alkaline electroplating bath consisting of a mixture of (Cu(amine)) and (Cu(Nl-l,,) complexes, in which the (Cu(NH complex is in a proportion of -30 percent and preferably between .14 percent and percent, leads to a plating of copper on aluminum with a very goodadherence and a current efficiency in the neighborhood of 100 percent. This unexpected result represents an important progress in the art of electroplating copperon aluminum. The electroplating operation is carried out in conventional manner, namely by immersion of an aluminum workpiece to be planted into the plating bath mentioned above and passing an electric current through this bath between the workpiece as' cathode and an anode.

It should be noted that the workpiece to be plated in accordance with the present invention can be of pure aluminum metal or of a commercial aluminum containing the usual impurities inherent to its manufacture or still of an aluminum alloy of any desired composition.

The plating bath of the present invention has normally a pH of approximately 8 to 13 and preferably in the range of 9 to 12.

The nature of the divalent copper salt present in the bath of this invention is of little importance, however, the salt must be such that cupric ions are produced when the salt is dissolved in water. Suitable salts are, for instance, copper nitrate, copper sulfate, copper acetate, copper chloride, etc. The amount of divalent copper salt may vary within wide limits depending on the salt employed as well as on the other substances contained in the bath and on the plating conditions, such as current density, desired thickness of copper deposit, and the like. Generally, the amounts vary so as to obtain cupric ion concentrations between '13 and 105 grams per litre of the bath and preferably between 26 and 78 grams per litre of the bath. As examples of amines which can be used in the plating of the present invention, one can cite the primary, secondary, and tertiary aliphatic amines such as acyclic lower alkyl amines, e.g., ethylamine, diethylamine, and triethylamine, and their substituted derivatives such as alkanolamines, e.g., triethanolamine, and also polyamines, e.g., ethylenediamine, diethylenetriamine and tetraethylene-pentamine. Cycloaliphatic amines, such as hexamethylenetetramine and triethylenetetramine as well as aromatic amines such as pyridine and its derivitives are also suitable.

The employed amine has preferably at least two nitrogen atoms and should be capable of forming a complex with cupric ions in solution.

Ammonia which plays a key role in the electroplating bath of this invention, is present in said aqueous bath in the form of ammonium hydroxide. In fact, it can be added to the bath in the form of commercial ammonium hydroxide, namely-an aqueous solution of about 30 percent by weight ammonia, or in the form of any desired concentration.Obviously, pure ammonia can also be added into the bath in which it will be transformed in situ into ammonium hydroxide.

The mixture of amine and ammonia, the latter being in the form of ammonium hydroxide, constitutes the complexing agent for the cupric ions and the amount of this agent must be at least sufficient to complex the cupric ions provided during dissolution of the copper salt. It is, however, preferable to have a small excess of ammonium hydroxide, whereby it can also be used to maintain thepl-l at a desired level. The amount of each ingredient forming the-complexing agent must however be such that the copper-ammonia complex which is formed in the bath is in a proportion of between 10 and 30 percent and preferably between 14 and 25 percent with respect to the total quantity of the complex ions existing in the bath. As a specific example of effective quantities, one can use between 50 and 500 grams of tetraethylenepentamine per litre of the bath, perferably between 100 and 300 grams per litre, and also between 7 and 160 ml of ammonium hydroxide of 30 percent by weight ammonia, per litre of the bath, the preferred amounts of ammonium hydroxide being between 15 and 100 ml per litre. The amounts of the amine must be generally be sufficient to complex to 90 percent and preferably to 86 percent of the divalent cupric ions present in the solution.

Further introduction into the bath of a source of fluoride ions (F), for instance, in the form of sodium, potassium or ammonium salt, preferably in the form of NIH F, in a concentration of 2 to 7 percent of the amount of the copper salt in the bath, leads to an additional improvement of adherence.

The use in the bath of an ammonium salt such as NH NO Nl-LCll, (Ni-1.0 etc., in addition to ammonia itself, may improve the color and brightness of the copper deposit, however, at the expense of the adherence. If these salts are used instead of ammonia or of the amine, thre is obtained a substantial reduction of the adherence and of the current efficiency. The same happens when ammonia is replaced by another base such as sodium hydroxide. It is therefore obvious that in order to obtain the beneficial results of the present invention, it is essential that ammonia and the amine be present in the above indicated proportions.

The plating bath according to the present invention may also contain other conventional compounds and additives such as wetting agents, brightening agents and the like.

The other conditions of the plating operation are generally the same as those usually employed in this type of process. For instance, the temperature of the bath will generally be in the range of 25 to 90 and preferably between 25 and 30C. The operating voltage between the workpiece used as cathode and an anode is in the range of 5 to 25 volts depending on the current density used, the latter being generally in the range of to 400 amperes per square foot. It is also advantageous to agitate the bath vigorously particularly if one wishes to achieve the upper limits of the current density. Mechanical agitation is used because an agitation with compressed air would produce rapid loss of NH in the bath which, of course, is undersirable.

It has also been found that the process according to the present invention can be applied with particular advantage to a continuous plating of wires, strips, sheets and other flexible aluminum objects forming the cathode and continuously passing at a predetermined speed in the bath between anodes, for instance, of copper. For this purpose, the aluminum wires, strips or the like are unwound from a bobbin at one end or the bath and after passing in the bath where copper is directly plated thereon, they are removed from the bath at the opposite end and are wound on another bobbin or roller in the form of a final product ready to be placed on the market. This is a novel and advantageous feature of the present invention which, to our knowledge, has never yet been accomplished in a satisfactory manner on an industrial scale.

In this way, aluminum articles are provided with copper deposits which are uniform, bright and adherent at apeeds up to and in excess of 30 ft/min.; the thickness of the deposit may easily reach 12.5,u.. The resulting copper plated wires, strips, sheets and the like, even when the thickness of the copper layer thereon is realtively low (for instance between 1.0 and 5.0g.) can be soldered, brazed or welded with exceptional ease, as if they were made entirely of copper. This is contrary, however, to the well known difficulty encountered in soldering, brazing or welding of aluminum objects in view of the oxide layer present thereof. Obviously, therefore, the plated products of the present invention exhibit considerable industrial and commercial advantages.

It should also be noted that the aluminum workpiece to be plated in accordance with the present invention is preferably subjected to an initial cleaning or degreasing treatment to improve the adherence of the copper deposit. Several such preconditioning procedures are known in the art, however, the one which is preferred is the following:

1. Passing the aluminum workpiece to be treated in an alkaline bath for about 10 to seconds. The bath is preferably at about 60C.

2. Rinsing in water (cold).

3. Passing the article in an acid bath for about 3 to 5 seconds. The bath is preferably at a temperature of 60C.

4. Rinsing with water (cold).

5. Passing the article again in an alkaline bath for approximately 3 seconds. The temperature of the bath is about 60C.

6. Rinsing with water (cold).

7. Passing the workpiece in the plating bath according to the present invention.

All these operations may easily be carried out continuously.

The alkaline baths mentioned above may consist, for instance, of an aqueous solution of NaOH and the acid bath may be a solution of HCl.

As mentioned above, the cleaning and degreasing operations of this type, carried out before the actual plating, are generally known in the art and it is therefore unnecessary to describe them in greater detail. The concentrations of the alkaline and acid baths, the time during which the workpiece is passed therethrough, the temperatures of the baths, etc., will be easily adjusted by the man of the art so as to obtain optimum results. Obviously, otehr alkaline baths, such as those based on sodium bicarbonate, and other acid baths, such as those based on nitric acid, may be used and the invention is not liimited to the pretreatments that could be employed before plating.

It should also be noted that the plating bath according to the present invention is generally stable and easy to control, producing entirely reproducible results. The pH of the bath can easily be checked from time to time and when it decreases due to evaporation of ammonia, it suffices to add a little ammonia to bring it back to the desired level. This ammonia addition into the plating bath, to maintain the pH at a predetermined level, is usually carried out at predetermined intervals and presents no difficulty whatsoever.

It has been found that the preferred composition of the plating bath in accordance with the present invention comprises copper nitrate Cu(NO as the divalent copper salt, tetraethylenepentamine as the amine and ammonium hydroxide NH OH at about 30 percent by weight Nl-l as the ammonia portion of the bath. Further addition of a small quantity of ammonium fluoride NH E is also preferred.

The following examples, based on a specific bath composition, but without limiting the present invention thereto, are given hereinafter for illustration purposes.

EXAMPLE 1 A plating bath comprising only copper nitrate and tetraethylenepentamine in the following proportions has been prepared:

Cu(NO 3H 20 150 grams per litre tetraethylenepentamine-in the range from 137 grams per litre to 167 grams per litre current density72 to 400 amp/foot Aluminum wire was plated in this bath in a continuous manner as already described above in the descriptive portion of this application. The obtained deposit was found non adherent and the maximum current efficiency was 16.6 percent. The pH of the bath varied between 9.5 and 10.65. At lower current densities, only a portion of the aluminum wire was plated.

EXAMPLE 2 A bath consisting only of a copper salt and of ammonia in the following proportions have been prepared:

Cu(NO 3H Ol50 grams per litre Nl-LOH (solution of approximately 30% by weight of ammonia)200 ml per litre current densityin the range between and 450 amp/foot At a low current density, a black smut layer appeared on the aluminum workpiece. However, at 450 amp- /foot a very hard and brittle layer of copper was deposited on aluminum. A pH of 12 was used.

EXAMPLE 3 A bath according to the present invention having the following composition was prepared:

Cu(NO 3H O -300 grams per litre tetraethylenepentamine-268 ml NH.,OI-l (28 to 30% Nl-l 86 ml current densityin the range from 12 to 400 amp/foot The copper deposit obtained using this bath to plate continuouslyan aluminum wire exhibited a regular and adherent layer of copper which was neither too hard nor too brittle. The pH was from 10.5 to 11 and the current efficiency in the neighborhood of 100 percent. During plating the bath was subjected to a vigorous mechanical agitation.

When a small amount of Nl-LF (between 2 and 4 grams per litre) was added to the bath, the copper layer became even more adherent.

The aluminum workpiece thus plated with a layer of copper having a thickness generally in the range of 0.2 and 125 and preferably between 0.5 and Sp.can be soldered, brazed or welded without any difficulty contrary to objects made solely of aluminum. Such plated workpiece, particularly in the form of wire, strip, or sheet, has therefore considerable advantages over the same articles made solely of aluminum.

Other plating baths having slightly different compositions and ingredients then those mentioned in example 3 hereinabove but falling within the limits of the present invention as described in the specification, have been found to give similar advantageous results.

Finally, the aluminum workpiece plated with'copper in accordance with the present invention may be subjected to additional plating operations whereby zinc, tin, nickel or other metals may be plated on the copper layer. Plating of such various metals on copper is easily accomplished, although it is very difficult to plate them on aluminum.

It is therefore clear that the invention is not limited to the specific examples and embodiments described above but that various modifications obvious to those skilled in the art may be made without departing from the spirit of this invention.

We claim:

1. A method of electroplating copper directly on aluminum which comprises immersing an aluminum workpiece in an aqueous alkaline plating bath containing a divalent copper salt and a complexing agent consisting of a mixture of an amine and ammonia, capable of forming (Cu(amine)) and (Cu(NH complexes, the amounts of the amine and ammonia being such that together they are at least sufficient to complex all cupric ions provided by the divalent copper salt and the amount of the (Cu(NH complex being from to 30 percent of the total complex ions present in the bath, the bath having a pH in the range of 8 to 13, and passing an electric current through the bath between the almunium workpiece as cathode and an anode, said electric current being of sufficient density to effect desired deposit of copper on aluminum.

2. Method according to claim 1, in which the divalent copper salt is selected from the group consisting of copper nitrate, copper sulfate, copper acetate and copper chloride.

3. Method according to claim 1, in which the aqueous alkaline bath contains an amount of divalent copper salt which is sufficient to form in solution cupric ions in a concentration of 13 to 105 grams per litre.

4. Method according to claim 1, in which the divalent copper salt is selected from the group consisting of copper nitrate, copper sulfate, copper acetate, and copper chloride and the amount thereof is such as to form in solution cupric ions in a concentration between 26 and 78 grams per litre.

5. Method according to claim 1, in which the amine is a primary, secondary, or tertiary amine having more than two nitrogen atoms and capable of forming a complex with the cupric ions in solution.

6. Method according to claim 1, in which the amine is selected from the group consisting of ethylamine, diethyamine, triethylarnine, triethanolamine, ethylenediamine, diethylene-triamine, tetraethylenepentamine, hexamethylenetetramine, triethylenetetramine and pyridine.

7. Method according to claim 1, in which ammonia is in the form of commercial ammonium hydroxide containing about 30 percent by weight of ammonia.

8. Method according to claim 1, in which the aqueous alkaline bath contains a quantity of amine sufficient to complex to percent of the divalent cupric ions in solution and contains from 7 to 160 ml of ammonia per litre of bath, in the form of ammonium hydroxide of about 30 percent by weight ammonia.

9. Method according to claim 1, in which the aqueous alkaline bath contains a quantity of amine sufficient to complex 75 to 86 percent of divalent cupric ions in solution and contains between 15 and ml of ammonia per litre of bath, in the form of ammonium hydroxide of about 30 percent by weight ammonia.

10. Method according to claim 1, in which the aqueous alkaline bath contains 50 to 500 grams of tetraethylene-pentamine per litre and 7 to ml of ammonia per litre, the latter being in the form of ammonium hydroxide of about 30 percent by weight ammonia.

11. Method according to claim 1, in which the aqueous alkaline bath contains between 100 and 300 grams of tetraethylenepentamine per litre and between 15 and lOO ml of ammonia per litre, the latter being in the form of ammonium hydroxide of about 30 percent by weight ammonia.

12. Method according to claim 11', in which the (Cu(NH H complex is in a proportion of between 14 and 25% of the total complex ions present in the aqueous alkaline bath.

13. Method according to claim 1, in which the pH of the aqueous alkaline bath is in the range between 9 and 12.

14}. Method according to claim 1, in which the pH of the aqueous alkaline bath is maintained at a predetermined level during the entire plating operation by intermittent addition of ammonium hydroxide.

1'5.'Method according to claim 1, in which the temperature of the aqueous alkaline bath is between 25 and 90C.

16. Method according to claimll, in which the temperature of the aqueous alkaline bath is between 25 and 30C.

17. Method according to claim 1, in which the current density is in the range between 10 and 400 amplfoot".

18. Method according to claim 1, in which the aluminum workpiece is subjected to a degreasing and clean- 7 ing pretreatment prior to its immersion into the plating bath.

19. Method according to claim 1, in which a small quantity of a source of fluoride ions is also introduced into the plating bath.

20. Method as claimed in claim 1, in which a small quantity of a source of fluoride ions in the form of sodium, potassium, or ammonium salt, is also introduced into the plating bath.

21. Method according to claim 1, in which a source of fluoride ions in the form of Nl-LF and in the amount of 2 to 7 percent of the amount of divalent copper salt, is also introduced into the plating bath.

22. Method according to claim 1, in which the divalent copper salt is copper nitrate Cu(NO the amine is tetraethylenepentamine and ammonia is in the form of commercial ammonium hydroxide.

23. Method according to claim 1, in which the divalent copper salt is copper nitrate Cu(NO the amine is tetraethylenepentamine, and ammonia is in the form of commercial ammonium hydroxide, and there is additionally introduced a small amount of fluoride.

24. A continuous method of electroplating copper directly on wires, strips, sheets and other flexible workpieces of aluminum, which comprises continuously forwarding the workpiece at a predetermined speed through an aqueous alkaline plating bath containing a divalent copper salt and a complexing agent consisting of a mixture of an amine and ammonia, capable of forming (Cu(amine)) and (Cu(NH complexes, the amounts of the amine and ammonia being such that together they are at least sufficient to complex all cupric ions provided by the divalent copper salt and the amount of the (Cu(Nl-l complex being from to 30 percent of the total complex ions present in the bath, the bath having a pH in the range of 8 to 13, and passing an electric current through the bath between the aluminum workpiece continuously travelling through the bath as cathode and an anode, said electric current being of sufficient density to effect desired deposit of copper on the aluminum workpiece while the latter travels through the bath.

25. Method according to claim 24, in which the divalent copper salt is selected from the group consisting of copper nitrate, copper sulfate, copper acetate and copper chloride.

26. Method according to claim 24, in which the divalent copper salt is selected from the group consisting of copper nitrate, copper sulfate, copper acetate, and copper chloride and the amount thereof is such as to form in solution cupric ions in a concentration between 26 and 78 grams per litre.

27. Method according to claim 24, in which the amine is a primary, secondary, or tertiary amine having more than two nitrogen atoms and capable of forming a complex with the cupric ions in solution.

28. Method according to claim 24, in which the amine is selected from the group consisting of ethylamine, diethyamine, triethylamine, triethanolamine, cthylenediarnine, diethylenetriamine, tetraethylenepentamine. hexamethylenetetramine, triethylenetetramine and pyridine.

29. Method according to claim 24, in which ammonia is in the form of commercial ammonium hydroxide containing about 30 percent by weight of ammonia.

30. Method according to claim 24, in which the aqueous alkaline bath contains a quantity of amine sufficient to complex to percent of divalent cupric ions in solution and contains from 7 to 160 ml of ammonia per litre of bath, in the form of ammonium hydroxide of about 30 percent by weight ammonia.

31. Method according to claim 24, in which the aqueous alkaline bath contains a quantity of amine sufficient to complex 75 to 86 percent of divalent cupric ions in solution and contains between 15 and ml of ammonia per litre of bath, in the form of ammonium hydroxide of about 30 percent by weight ammonia.

32. Method according to claim 24, in which the aqueous alkaline bath contains 50 to 500 grams of tetraethylene-pentamine per litre and 7 to ml of ammonia per litre, the latter being in the form of ammonium hydroxide of about 30 percent by weight ammonia.

33. Method according to claim 24, in which the aqueous alkaline bath contains between 100 and 300 grams of tetraethylenepentamine per litre and between 15 and 100 ml of ammonia per litre, the latter being in the form of ammonium hydroxide of about 30 percent by weight ammonia.

34. Method according to claim 24, in which the (Cu(NH complex is in a proportion of between 14 and 25 percent of the total complex ions present in the aqueous alkaline bath.

35. Method according to claim 24, in which the pH of the aqueous alkaline bath in the range of 8 to 13.

36. Method according to claim 24, in which the pH of the aqueous alkaline bath is in the range between 9 and 12.

37. Method according to claim 24, in which the pH of the aqeuous alkaline bath is maintained at a predetermined level during the entire plating operation by intermittent addition of ammonium hydroxide.

38. Method according to claim 24, in which the temperature of the aqueous alkaline bath is between 25 and 90C. 1

39. Method according to claim 24, in which the temperature of the aqueous alkaline bath is between 25 and 30C.

40. Method according to claim 24, in which the current density is in the range between 10 and 400 amplfoot 41. Method according to claim 24, in which the aluminum workpiece is subjected to a degreasing and cleaning pretreatment prior to its immersion into the plating bath.

42. Method according to claim 24, in which a small quantity of a source of fluoride ions is also introduced into the plating bath.

43. Method as claimed in claim 24, in which a small quantity of a source of fluoride ions in the form of sodium, potassium, or ammonium salt, it also introduced into the plating bath.

44. Method according to claim 24, in which a source of fluoride ions in the form of NH F and in the amount of 2 to 7 percent of the amount of divalent copper salt, is also introduced into the plating bath.

45. Method according to claim 24, in which the continuous process is carried out at a speed up to and in excess of 30 feet/minute.

46. Method according to claim 24, in which the divalent copper salt is copper nitrate Cu(NO the amine is tetraethylenepentamine and ammonia is in the form of commercial ammonium hydroxide.

47. Method according to claim 24, in which the divalent copper salt is copper nitrate Cu(NO the amine plex all cupric ions provided by the divalent copper salt and the amount of the (Cu(NH H complex being from 10 to 30 percent of the total complex ions present in the bath, the bath having a pH in the range of 8 to 13.

49. An aqueous alkaline electroplating bath according to claim 48, in which the amount of the (Cu(NH complex is from 14 to 25 percent of the total complex ions present in the bath.

. UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,775,264 Dated November 27th, 1973 Nanabhai Rustomji Bharucha and Inventr(s) Mohammad Barakat Ilahi Janjua It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading of the patent, line 2, change "Nanbhai" to Nanabhai. Column 1, line 20, after "comprising" insert -a--'; line 37, change "planted" to --plated-; line 43, after "of" delete "a"; line 63, after "plating" insert -bath-.

Column 2, line 40, before "generally" delete "be"; line 54, change "thre" to -there--. Column 3,- line 1, after"'90" insert -C-; line '20, change "or" to -of-; line 31, change "apeeds" to speeds; line40, change "thereof" to thereon. Column 4, line 12, change "otehr" to other--; line 35, change "NH E" to NH F--; line 44 change "3H t0 3H O; line 57 change "have" to -'-has-. Column 5, line 6, change "NH to --NH line 22, change "Sucan to Su, can-'; line 52, chang "(Cu(NH to -(Cu(NH line 56, change "(Cu(NH to (Cu (NH line 60, change "almunium" to aluminum-. Column 7, line 22, after "of" insert --ammonium-; after line 46 insert the following claim 26. Method according to claim 24-, in which the aqueous alkaline bath containsan amount of divalen copper salt which is sufficient to form in' solution cupric ions in a concentration of 13 to 1 05 grams per litre.; line 47, change "26" to ,--27; line 53, change "27" to --28 line 57, change "28" to 29--; line 63, change "29" to' -,-30-; line 66, change "30" to 3l--. Column 8, line 5, change "31" to -32; linell, change "32" to -33--; line 16, change "33" to -'-34--; line 22, change "34" to --(35.----; delete lines 26'and 27 (Claim 35 in their entirety; line 54, change "it" to -'-is--. Column 10, line 7, change "(Cu(NH )"to --(Cu(NH line 8, delete n II Signed and sealed this 30th day of April 197A.

(SEAL) Attest:

EDWARD I- I.FLE TCPER,JR. G. E'iARSHALL ZJANN Attesting Officer Commissionerof Patents FORM PO-O (10-69) uscoMM-Dc scan-Poo I I .5. GOVERNMENT PRINTING OFFICE lll l O-JUI-JSI 

2. Method according to claim 1, in which the divalent copper salt is selected from the group consisting of copper nitrate, copper sulfate, copper acetate and copper chloride.
 3. Method according to claim 1, in which the aqueous alkaline bath contains an amount of divalent copper salt which is sufficient to form in solution cupric ions in a concentration of 13 to 105 grams per litre.
 4. Method according to claim 1, in which the divalent copper salt is selected from the group consisting of copper nitrate, copper sulfate, copper acetate, and copper chloride and the amount thereof is such as to form in solution cupric ions in a concentration between 26 and 78 grams per litre.
 5. Method according to claim 1, in which the amine is a primary, secondary, or tertiary amine having more than two nitrogen atoms and capable of forming a complex with the cupric ions in solution.
 6. Method according to claim 1, in which the amine is selected from the group consisting of ethylamine, diethyamine, triethylamine, triethanolamine, ethylenediamine, diethylene-triamine, tetraethylenepentamine, hexamethylenetetramine, triethylenetetramine and pyridine.
 7. Method according to claim 1, in which ammonia is in the form of commercial ammonium hydroxide containing about 30 percent by weight of ammonia.
 8. Method according to claim 1, in which the aqueous alkaline bath contains a quantity of amine sufficient to complex 70 to 90 percent of the divalent cupric ions in solution and contains from 7 to 160 ml of ammonia per litre of bath, in the foRm of ammonium hydroxide of about 30 percent by weight ammonia.
 9. Method according to claim 1, in which the aqueous alkaline bath contains a quantity of amine sufficient to complex 75 to 86 percent of divalent cupric ions in solution and contains between 15 and 100 ml of ammonia per litre of bath, in the form of ammonium hydroxide of about 30 percent by weight ammonia.
 10. Method according to claim 1, in which the aqueous alkaline bath contains 50 to 500 grams of tetraethylene-pentamine per litre and 7 to 160 ml of ammonia per litre, the latter being in the form of ammonium hydroxide of about 30 percent by weight ammonia.
 11. Method according to claim 1, in which the aqueous alkaline bath contains between 100 and 300 grams of tetraethylenepentamine per litre and between 15 and 100 ml of ammonia per litre, the latter being in the form of ammonium hydroxide of about 30 percent by weight ammonia.
 12. Method according to claim 1, in which the (Cu(NH3)4) complex is in a proportion of between 14 and 25% of the total complex ions present in the aqueous alkaline bath.
 13. Method according to claim 1, in which the pH of the aqueous alkaline bath is in the range between 9 and
 12. 14. Method according to claim 1, in which the pH of the aqueous alkaline bath is maintained at a predetermined level during the entire plating operation by intermittent addition of ammonium hydroxide.
 15. Method according to claim 1, in which the temperature of the aqueous alkaline bath is between 25* and 90*C.
 16. Method according to claim 1, in which the temperature of the aqueous alkaline bath is between 25* and 30C.
 17. Method according to claim 1, in which the current density is in the range between 10 and 400 amp/foot2.
 18. Method according to claim 1, in which the aluminum workpiece is subjected to a degreasing and cleaning pretreatment prior to its immersion into the plating bath.
 19. Method according to claim 1, in which a small quantity of a source of fluoride ions is also introduced into the plating bath.
 20. Method as claimed in claim 1, in which a small quantity of a source of fluoride ions in the form of sodium, potassium, or ammonium salt, is also introduced into the plating bath.
 21. Method according to claim 1, in which a source of fluoride ions in the form of NH4F and in the amount of 2 to 7 percent of the amount of divalent copper salt, is also introduced into the plating bath.
 22. Method according to claim 1, in which the divalent copper salt is copper nitrate Cu(NO3)2, the amine is tetraethylenepentamine and ammonia is in the form of commercial ammonium hydroxide.
 23. Method according to claim 1, in which the divalent copper salt is copper nitrate Cu(NO3)2, the amine is tetraethylenepentamine, and ammonia is in the form of commercial ammonium hydroxide, and there is additionally introduced a small amount of fluoride.
 24. A continuous method of electroplating copper directly on wires, strips, sheets and other flexible workpieces of aluminum, which comprises continuously forwarding the workpiece at a predetermined speed through an aqueous alkaline plating bath containing a divalent copper salt and a complexing agent consisting of a mixture of an amine and ammonia, capable of forming (Cu(amine)) and (Cu(NH3)4) complexes, the amounts of the amine and ammonia being such that together they are at least sufficient to complex all cupric ions provided by the divalent copper salt and the amount of the (Cu(NH3)4) complex being from 10 to 30 percent of the total complex ions present in the bath, the bath having a pH in the range of 8 to 13, and passing an electric current through tHe bath between the aluminum workpiece continuously travelling through the bath as cathode and an anode, said electric current being of sufficient density to effect desired deposit of copper on the aluminum workpiece while the latter travels through the bath.
 25. Method according to claim 24, in which the divalent copper salt is selected from the group consisting of copper nitrate, copper sulfate, copper acetate and copper chloride.
 26. Method according to claim 24, in which the divalent copper salt is selected from the group consisting of copper nitrate, copper sulfate, copper acetate, and copper chloride and the amount thereof is such as to form in solution cupric ions in a concentration between 26 and 78 grams per litre.
 27. Method according to claim 24, in which the amine is a primary, secondary, or tertiary amine having more than two nitrogen atoms and capable of forming a complex with the cupric ions in solution.
 28. Method according to claim 24, in which the amine is selected from the group consisting of ethylamine, diethyamine, triethylamine, triethanolamine, ethylenediamine, diethylenetriamine, tetraethylenepentamine, hexamethylenetetramine, triethylenetetramine and pyridine.
 29. Method according to claim 24, in which ammonia is in the form of commercial ammonium hydroxide containing about 30 percent by weight of ammonia.
 30. Method according to claim 24, in which the aqueous alkaline bath contains a quantity of amine sufficient to complex 70 to 90 percent of divalent cupric ions in solution and contains from 7 to 160 ml of ammonia per litre of bath, in the form of ammonium hydroxide of about 30 percent by weight ammonia.
 31. Method according to claim 24, in which the aqueous alkaline bath contains a quantity of amine sufficient to complex 75 to 86 percent of divalent cupric ions in solution and contains between 15 and 100 ml of ammonia per litre of bath, in the form of ammonium hydroxide of about 30 percent by weight ammonia.
 32. Method according to claim 24, in which the aqueous alkaline bath contains 50 to 500 grams of tetraethylene-pentamine per litre and 7 to 160 ml of ammonia per litre, the latter being in the form of ammonium hydroxide of about 30 percent by weight ammonia.
 33. Method according to claim 24, in which the aqueous alkaline bath contains between 100 and 300 grams of tetraethylenepentamine per litre and between 15 and 100 ml of ammonia per litre, the latter being in the form of ammonium hydroxide of about 30 percent by weight ammonia.
 34. Method according to claim 24, in which the (Cu(NH3)4) complex is in a proportion of between 14 and 25 percent of the total complex ions present in the aqueous alkaline bath.
 35. Method according to claim 24, in which the pH of the aqueous alkaline bath in the range of 8 to
 13. 36. Method according to claim 24, in which the pH of the aqueous alkaline bath is in the range between 9 and
 12. 37. Method according to claim 24, in which the pH of the aqeuous alkaline bath is maintained at a predetermined level during the entire plating operation by intermittent addition of ammonium hydroxide.
 38. Method according to claim 24, in which the temperature of the aqueous alkaline bath is between 25* and 90C.
 39. Method according to claim 24, in which the temperature of the aqueous alkaline bath is between 25* and 30C.
 40. Method according to claim 24, in which the current density is in the range between 10 and 400 amp/foot2.
 41. Method according to claim 24, in which the aluminum workpiece is subjected to a degreasing and cleaning pretreatment prior to its immersion into the plating bath.
 42. Method according to claim 24, in which a small quantity of a source of fluoride ions is also introduced into the plating bath.
 43. Method as claimed in claim 24, in which a small quantity of a source of fluoride ions in the form of sodium, potassium, or ammonium salt, it also introduced into the plating bath.
 44. Method according to claim 24, in which a source of fluoride ions in the form of NH4F and in the amount of 2 to 7 percent of the amount of divalent copper salt, is also introduced into the plating bath.
 45. Method according to claim 24, in which the continuous process is carried out at a speed up to and in excess of 30 feet/minute.
 46. Method according to claim 24, in which the divalent copper salt is copper nitrate Cu(NO3)2, the amine is tetraethylenepentamine and ammonia is in the form of commercial ammonium hydroxide.
 47. Method according to claim 24, in which the divalent copper salt is copper nitrate Cu(NO3)2, the amine is tetraethylenepentamine, and ammonia is in the form of commercial ammonium hydroxide, and there is additionally introduced a small amount of ammonium fluoride.
 48. An aqueous alkaline electroplating bath comprising a divalent copper salt and a complexing agent con-sisting of a mixture of amine and ammonia, capable of forming (Cu(amine)) and (Cu(NH3)4) complexes, the amounts of the amine and ammonia being such that together they are at least sufficient to complex all cupric ions provided by the divalent copper salt and the amount of the (Cu(NH3)4) complex being from 10 to 30 percent of the total complex ions present in the bath, the bath having a pH in the range of 8 to
 13. 49. An aqueous alkaline electroplating bath according to claim 48, in which the amount of the (Cu(NH3)4) complex is from 14 to 25 percent of the total complex ions present in the bath. 